Fabrication and Study of Properties of Graphene-Doped PMN-xPT Flexible Piezoelectric Thin Films

Conventional rigid sensors are often limited by their heavy weight and constrained structures, whereas flexible composite piezoelectric film sensors offer advantages of light weight and excellent mechanical properties; however, traditional flexible piezoelectric film sensors typically involve high fabrication costs and complex processes. This study aimed to develop a high-performance flexible piezoelectric film using a simple, low-cost method, fabricating a film based on lead magnesium niobate–lead titanate (PMN-xPT) piezoelectric ceramic powder, high-electron-mobility graphene (Gr), and a polydimethylsiloxane (PDMS) flexible substrate (0.67PMN-0.33PT-Gr/PDMS), following a "piezoelectric phase–conductive phase–flexible matrix" ternary composite design. PMN-xPT ceramic powder, synthesized via a two-step solid-state reaction to suppress the pyrochlore phase, was combined with graphene and mixed into PDMS to form an aluminum electrode/(0.67PMN-0.33PT-Gr/PDMS)/ITO-PET composite film structure, wherein PMN-xPT serves as the piezoelectric phase providing polarization charges, graphene acts as the conductive phase forming a network that significantly reduces bulk resistance and promotes charge collection and transport, and PDMS functions as the flexible matrix that withstands strain and effectively transfers stress to the piezoelectric particles. Experimentally, the flexible piezoelectric film effectively converted human motion, such as finger bending, into electrical signals, generating a high output voltage of 7.7 V and a current response of 120 nA, which represents a 2.95-fold increase in voltage and a 3-fold increase in current compared to the film without graphene. After 1000 repeated bending cycles, the output voltage remained stable at 7.7 V±0.2 V (fluctuation≤±2.6%) and the output current was maintained at 120 nA±5 nA (fluctuation≤±4.2%), demonstrating excellent mechanical durability. This flexible, high-performance piezoelectric film thus provides an effective solution for developing self-powered wearable motion sensors, health monitoring equipment, and medical implantable sensors.